how do you print from dos programs on dell 510 with a computer that needs a parrallel port ?

Hi Guys

    I recently bought a dell 510 computer when I went to try to attach my hp4si printer I noticed that the computer did not have a parrarell port so I could not attach the printer. I went to a computer store and bought  a cable that was able to connect to the printer and use a usb port on computer. It works with windows based programs but I cant seem to print from dos programs. Anybody have any Ideas?

                        Thanks

                         Sam